1815, of machinery, "reaction of wheels on each other produced by an inconstant load," from back (adj.) + lash (n.) "a blow, stroke." In metaphoric sense, it is attested from 1929.
there was a backlash of intolerance
the political movie backlashed on the Democrats
background
backhand
backhanded
backhoe
backing
backlash
backless
backlist
backlog
backorder
backpack
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